Tanana Alaska State Soil Soil Science Society of America Introduction Many states have a designated state bird, flower, fish, tree, rock, etc. And, many states also have a state soil – one that has significance or is important to the state. The Tanana is the official state soil of Alaska. Let’s explore how the Tanana is important to Alaska. History The Tanana series is found only in Alaska and was established in the Yukon-Tanana Area in 1914. It was named after the Tanana River, whose name in-turn was derived from the Athabaskan word for “Mountain River.” The Tanana soil was chosen by Alaskan soil scientists because it is a permafrost soil, a property in the United States that is unique to Alaska. Tanana soils range widely through the interior of Alaska and when cleared can thaw and become productive farm land. What is Tanana Soil? Under mature native vegetation, Tanana soils are poorly drained and contain per- mafrost within 50 inches of the surface. If the surface vegetation and organic mat is disturbed, either through wildfire or cultural activities such as farming, the soil will warm and become well drained. Tanana soils are on flood plains and alluvial terraces (a river terrace of alluvium-material transported and deposited by moving water- rather than carved in solid rock. When undisturbed and frozen, Tanana soils support a native plant community of black spruce, shrubs and feather moss. When thawed, white spruce and paper birch forests dominate. When cleared and developed for agriculture, Tanana soils are used for hay, pasture, small grains, and vegetables. Every soil can be separated into three separate size fractions called sand, silt, and clay, which makes up the soil texture. They are present in all soils in different propor- tions and say a lot about the character of the soil. Undisturbed, Tanana soils have an organic layer that ranges from 2 to 8 inches thick. This organic material is slightly to moderately decomposed and derived mostly from moss. The top soil is black mucky silt loam enriched with highly decomposed or- ganic material called humus. The sub soil is gray and light olive-brown stratified silt loam and very fine sandy loam that has streaks and pockets of black mucky material moved from above. These streaks and pockets are caused from a process called cryo- turbation. Cryoturbation, or frost churning, causes a mixing of soil horizons due to freezing and thawing. The subsoil of an undisturbed Tanana is permanently frozen silt loam and very fine sandy loam. This frozen soil limits root growth and also perch- es the water table causing the soil to be poorly drained. When disturbed, Tanana soils thaw, which allow free drainage and the soil becomes well-drained. Once thawed, deeper observation of the soil can be made and a sandy and gravelly substratum can sometimes be found, usually below 3 feet (Figure 1). Photo Soil Monolith: Chip Clark/Smithsonian Institution Fig. 2. Location of the Tanana soil in Alaska. Credit: Smith- sonian Institution’s Forces of Change. Fig. 3 Alaskan Cabbage from Tanana Valley Fair. Credit: Alaska USDA-NRCS. Fig. 1. Thawing Tanana soil. Credit:Alaska USDA-NRCS. Where to dig Tanana Yes, you can dig a soil. It is called a soil pit and it shows you the ditions, wildlife habitat and recreational uses are plenty. When soil profile. The different horizontal layers of the soil are called altered, they support a forest of aspen, paper birch, and white soil horizons. This does not mean that other types of soil can- spruce which will also provide adequate habitat for wildlife and not be found there but that the Tanana is very common. Tanana recreation. When cultivated, Tanana soils are used for farming. soils exist in the interior of Alaska on the flood plains and low Due to nearly constant sunlight throughout the summer, some terraces of rivers. They occur in the Fairbanks North Star Bor- crops can grow to an enormous size. Examples include a 19 ough, Denali Borough, the Yukon-Koyukuk Census Area and the pound carrot, a 76 pound rutabaga, and a 106 pound cabbage Southeast Fairbanks Census Area (Figure 2). Tanana soil may (Figure 3). cover an estimated 3 to 5 million acres though a very small por- When Tanana soils are allowed to thaw and drain they have few tion of its range has actually been mapped. Most commonly, it limitations. The process changes the soil so drastically it actually will be found under a stunted black spruce forest, but if the site becomes a different soil. When thawed, Tanana typically changes has been disturbed, the forest may be white spruce and birch or to recognized soils Salchaket or Jarvis. Areas that were histori- being farmed. In all, there are a total of 561 named soils (series) cally Tanana soils now support homes, urban areas, roads and in Alaska. streets, parks, as well as agriculture Importance Limitations What makes the Tanana soil so important is its use and preva- When a soil cannot be used for one or more of the described lence in the State. When undisturbed, Tanana soils support a functions, it is referred to as a limitation. Soil experts, called Soil wetland forest of black spruce and shrubs that support an abun- Scientists, studied Tanana soil and identified that, under natural dance of wildlife and recreation. They are unique in that they conditions it has permafrost limitation. Permafrost in this soil are permanently frozen below 50 inches. Wild fire or human impedes the internal drainage causing the soil to be wet. The disturbance, such as plowing, will cause the soil to warm and dry, cold, hard layer of permafrost also limits the rooting depth for significantly altering its characteristics. After thawing, Tanana plants. Since this soil occurs on floodplains there is also risk soils support hay, grains, potatoes and cool season vegetables. of flooding. The restricted drainage make Tanana soils poorly suited for things such as trails, camp grounds and waste disposal. Uses Wind and water erosion are a concern on areas that have been cleared of native vegetation. In general, soils can be used for agriculture (growing foods, rais- ing animals, stables); engineering (roads, buildings, tunnels); ecology (wildlife habitat, wetlands), recreation (ball fields, play- ground, camp areas) and more. Tanana soils are important for all of these uses in Alaska. Under natural black spruce forest con- 2 Fig. 4. (Above) Extreme winter conditions under which Tanana soils develop. Credit:Alaska USDA-NRCS Staff, Brant Dallas.Fig. 5. (Above right) Black spruce and moss environment that greatly influence soil pH. Credit:Alaska USDA-NRCS Staff, Blaine Spellman. Fig. 6. (Inset) Young bull moose grazing on willow shrubs. Credit: Cory Cole Management In its natural state Tanana is typically managed for wildlife habitat exceed 90 degrees F (32 degrees C) while extreme winter and limited recreation. Tanana soils support a black spruce forest temperatures may dip below -60 degrees F (-51 degrees C). with an ericaceous (heather) shrub and moss understory. Animals The average annual precipitation is 12 inches (30 cm), with typically encountered include moose, grouse, snowshoe hares, and July and August being the wettest months and April the driest. many various song birds. The shrub layer provides many variet- Snow covers the ground continuously from October to late ies of wild berries including blue berries (Vaccinium uliginosum), April or early May. These strong freeze thaw cycles cause lingonberries (low bush cranberries)(Vaccinium vitis-idaea) and cryoturbation in the soil. cloud berries(Rubus chamaemorus). Common management strat- Organisms – This refers to plants and animal life. In the egies to protect against wind and water erosion are recommended soil, plant roots spread, animals burrow in, and bacteria break in areas where native vegetation has been cleared. down plant and animal tissue. These and other soil organisms speed up the breakdown of large soil particles into smaller Tanana Formation ones. Plants and animals also influence the formation and differentiation of soil horizons. Plants determine the kinds Before there was soil there were rocks and in between, CLORPT. and amounts of organic matter that are added to a soil under Without CLORPT, there will be no soil. So, what is CLORPT? normal conditions. Animals breakdown complex compounds It is the five major factors that are responsible for forming a soil into small ones and in so doing add organic matter to soil. Ta- like the Tanana series. It stands for Climate, Organisms, Relief, nana soils typically support a black spruce forest with a shrub Parent material and Time. CLORPT is responsible for the de- understory. These plants contribute organic acids to the soil velopment of soil profiles and chemical properties that differenti- causing the Tanana soil to be acid or have a low pH in its ate soils. So, the characteristics of Tanana (and all other soils) upper horizons (Figure 5). Common mammals in the area are determined by the influence of CLORPT. Weathering takes include brown and black bear, moose, wolf, lynx, furbearers place when environmental processes such as rainfall, freezing and rodents (Figure 6). Birds are attracted to the wet, boggy and thawing act on rocks causing them to dissolve or fracture forest for the plethora of insects to eat. Spruce hens and rough and break into pieces. CLORPT then acts on rock pieces, marine grouse also frequent to the area. sediments and vegetative materials to form soils. Relief – Landform position or relief describes the shape of the land (hills and valleys), and the direction it faces which Climate – Temperature and precipitation influence the rate at makes a difference in how much sunlight the soil gets and which parent materials weather and dead plants and animals how much water it keeps.